Process for manufacturing storage battery paste



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TREAT Wm-t CAC05 To Patented Oct. 15, 1940 2,211,814 FOB. MANUFACTUIEN (3i STORAGE BATTERY PAS l lmoeras PATENT OFFICE william c. Pritchard ma neben a. muy, Muncie, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation oi.' Delaware Application August 8, 1938, Serial No. 223,706

3 claim. (ci. 13e-zr) c I This inventionfrelates to addition agents to be used in' the manufacture of storage battery paste and is particularly concerned with a methody of extracting `such materials from waste sulphite y 5 liquors.`

vAn object of the invention is to provide a method whereby certain desirable constituents, such as yligno-sulphonic acid, in waste sulphite liquor maybe re'adily extracted therefrom for subsequent use as an addition agent. in the negative paste of storage battery plates, for giving 'the pl-ates increased life and capacity, particularly at low ambient temperatures. f

It is a further object of the invention to provide a method whereby the ligno-sulphonic acid may be inexpensively extracted inthe substantially pure state from waste sulphite liquor.

Further objects and advantages of the present invention will be apparent from the following description, wherein a preferred embodiment ofthe present invention is clearly shown.

Heretofore various substances have been pro-- posed as addition agents in storage battery paste, in an effort to obtain an improved paste' and 25 to the paste. Some of these substances are lignin, wood our, pulverized` leather, humic substances and many other organic and inorganicy compounds. Waste sulphite liquor has also been proposed as an addition agent, such liquor being the concentrated by-product of paper manufacture. The waste liquor is obtained from digestion of coniferous woods in a solution of calcium bisulphite and sulphurous acid. -The composition of waste sulphite liquor is extremely complex in nature deriving its constituents from practically all ingredients that are originally present in wood, with the exception of cellulose which is separated by iiltration after the diges- 40 tion of the woo in aforementioned solution. During this digestion step the sulphurous acid chemically acts upon the insoluble lignins, sugars, tannins, resins and carbohydrates to cause the same to go into solution. Thecombination oi' the calcium bi-sulphite and sulphurous acid also produces some organic calcium compounds.

In application Serial No. 173,863, assigned to the assignees of the present application, the use of l-igno-sulphonic acid is disclosed together with one method of separating'said acid in a substantially pure state from waste sulphite liquor. Our invention as contained herein is particularly directed to another method whereby ligno-sulphonic acid in the substantially pure state can thereby overcome undesirable properties inherent be readily and inexpensively extracted-from the l complex waste liquor. We havefound that ligno-sulphonic acid is the only desirable constituentin waste sulphite liquor rfor use as an addition agent in storage battery paste. yWe have further found .that the remaining compounds in 5 the waste sulphite liquor and particularly the calcium compounds are not only unnecessary in this addition agent, but are undesirable,` since they rdecrease the porosityL of the paste and `oi? the final active material. Stated diii'erently, the 10 active material formed by using waste Asulphite liquor as the addition agent thereto is more dense and therefore more costly, since a greater quantity of oxide of leadis necessary in themanu- -facture of the plates. Ligno-sulphonic acid in 15 the substantially pure state prepared according to the hereindescribed method is an ideal'addition agent for battery paste since the addition of the ligno-sulphonic acid does not decrease the porosity of the active materiaLof the plate and 90 hence does not increase the plate weight.

The single figure of the drawing is a chart dlagrammatically illustrating the process.

. The waste sulphite liquor of commerce is available on the marketin a sirupy form containing 2l about 50% water and about y50% solid. This condition is brought about by neutralization of the liquor, as it comes from the digestors, with either lime or magnesia to remove the excess sulphurous acid, filtering out this insoluble precipi- 30 tate and evaporating the filtrate to the desired consistency. In accordance with our invention, waste sulphite liquor of commerce is diluted with an equivalent quantity oi. water to produce a resultant solution containing about 25% total sol- 36 ids. Sulphuric acid having a specic gravity of about 1.400 is then added to the solution in sufficient quantity to bring the specific gravity of the mixture to about 1.300. Sulphuric acid reacts with calcium salts in waste sulphite liquor to 4o form a precipitate of calciumsulphate and set the ligne-sulphonic acid free inthe precipitated Y form, as well as precipitate any free ligno-sulphonic acid that is in solution. Ligno-sulphonic acid is insoluble in sulphuric acid solutions having a specic gravity approximating the gravity of the solution present. The compounds containing the sugars, tannins, carbohydrates, etc., re-

main in the solution in the dissolved state. The 50 salve the nano-mipnonic acid, the nitrate in both instances being discarded.

'I'he washed precipitate is next mixed with water, which dissolves out the ligno-sulphonic acid and leaves calcium sulphate as an insoluble.

residue. This solution is then filtered and the residue of calcium sulphate is then discarded.

The nitrate which consists of ligno-sulphonic' acid, water and a small amount of entrapped sulphuric acid may then be treated with an excess of calcium carbonate which reacts with the sulphuric acid to precipitate out as calcium sulphate. This l mixture and the amount introduced in conjunction with the ligno-sulpbonic acid is negligible.

The quantity of ligno-sulphonic acid solution to be used in the paste mixture varies in accordance of the concentration of the ligno-sulphonic acid therein. We have found that optimum conditions are obtained when using ligne-sulphonic acid in percentages from .05% to 1.0% based on the weight of the paste. It is our belief that this small percentage of ligno-sulphonic acid acts in effect as an addition agent ratherthan as an expander in the common use of the word. It prevents crystal growth of the lead particles of the negative plate at the beginning of formation and throughout the life of the plate. As far as wecandeterminethereisnoswellingorexpanding of the ligno-sulphonic acid itself.

While the embodiment of the present invention as herein disclosed, cnstitut a preferred form,

itis to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. A process for manufacturing storage battery paste comprising, treating waste sulphite liquor with a mineral acid to form a precipitate containing ligno-sulphonic acid, dissolving out the ligno-sulphonic acid from the precipitate by the action of water, and thereby separating substantially pure ligno-sulphonic acid from the in' tery paste.

3. The process described in claim 1 characterized by the addedstep of treating the substantially pure ligno-sulphonic acid with calcium carbonate for precipitating out excessive sulphuric acid prior to the step of mixing the substantially pure ligno-sulphonic acid with. lead oxide.

WILLIAM C. PRIICHARD. ROBERT A. DAILY.` 

